1. Field of the Invention
The present invention relates to battery monitoring and control systems and, more specifically, to a battery monitoring and control system with a wireless communication capability.
2. Description of the Related Art
Rechargeable batteries are used to power the electric vehicles (EVs), both in indoor and outdoor applications. Energy ratings of these batteries range from 0.5 kWh to 50 kWh for most vehicles. However, some electric vehicles use higher energy rated batteries. Batteries provide energy for the vehicle for propulsion. The stored energy in the battery is drained or discharged as the EV drives from one location to another. A typical EV design will have protocols and fuel gauging methods built into its system to determine the appropriate time to recharge the battery. The energy size of the battery is typically determined by the desired operating time of the electric vehicle. A battery's operating time usually has a direct relationship to the distance an EV can travel between re-charges and the load it carries.
The fundamental building block of a battery is referred to as a “cell.” Different chemistries form the basis of different types of cells. Some of the common chemistries are Lead Acid, Nickel-Cadmium (Ni-CD), Nickel Metal Hydride (Ni-MH), and Lithium ion (Li-ion). A battery is built with multiple cells that are connected in series and/or parallel to get a desired voltage and capacity. A multi-cell stack of connected cells is called a “cell stack.” Battery energy is a multiple of stack capacity and voltage.
Large size batteries in the kilo-Watt-hour (kWh) energy range are complex and may contain many electronic circuits to control and assist smooth functioning of a battery. Also, in some applications, several smaller independent batteries are connected in series and/or parallel to achieve multi-kWh batteries. In such scenarios, each of these independent batteries is called a “module.”
A module can operate independently and it typically consists of a cell stack and management circuitry referred to as a “battery management system” (BMS). The BMS may contain circuits used to measure the charge going into the battery during a charge step and the charge coming out of the battery during a discharge step. This process is generally referred to as “coulomb counting.” Coulomb counting is typically used to “fuel gauge” batteries.
A large size battery is constructed by combining many battery modules in parallel and/or in series to get the desired energy level (capacity times voltage). In such constructions there is a need to poll information contained in each of the modules to be supplied to the vehicle or to the charger. The term “charger” is a common term used in battery industry to charge a discharged battery.
Two sub-sets of electric vehicles include automatic guided vehicles (AGV), such as robotic transport vehicles, and human guided vehicles (MGV), such as pallet jacks and forklifts—both of which are typically indoor vehicles.
A control and communication module (CM) that is transposed between the battery modules and the vehicle and/or the charger carries out the functions of polling the data from each of the modules in the battery and supplying them to the vehicle or charger.
Typically, the required connections are implemented through a network of data cables. These cables can be cumbersome, costly, and inefficient, especially when many battery modules are involved.
Therefore, there is a need for a system to access battery data that does not use of physical cables connected to the battery.